NAME
synth - compute 1-d synthetic seismograms
SYNOPSIS
synth [ -Nvmod ] [ -OPotap1 ] [ -OUotap2 ] [ -ODotap3 ] [
-OTotap4 ] [ -nntpr ] [ -P ] [ -s ] [ -d ] [ -m_to_ft ] [
-ft_to_m ] [ -D ] [ -micro ] [ -gma ] [ -Ginput1 ] [ -prho-
gam ] [ -Cinput ] [ -L ] [ -Ttitle ] [ -lsnum ] [ -dtidelt ]
[ -c0ic0 ] [ -euiep ] [ -ediem ] [ -odndepth ] [ -olnlayer ]
[ -sdxa0 ] [ -rdxb0 ] [ -delsdxa ] [ -delrdxb ] [ -V ] [ -?
]
DESCRIPTION
synth computes synthetic seismograms based on 1-d layer cake
theory for arbitrary source and receiver depths. This tech-
nique permits running models having thousands of layers that
one gets from a log very quickly. Logs should be in the
form of depth (or layer thichness), velocity (or slowness),
and density. For each layer the velocity and density are
referenced to the bottom of the layer.
There are 2 ways to get paramerets into synth: (1) velocity
model contained in a disk file or brought in on stdin with
all the remaining parameters on the command line, or (2)
most of the model parameters contained in a disk file or
brought in on stdin with the few remaining parameters on the
command line. These arguments specify the output data set
names, optional traces per record, a file name containing
model parameters, and verbos printout, if desired. (see
Amoco report # F83-E-1)
Required Command line arguments
-OP, -OU, -OD, -OT otap1,2,3,4
Enter the output data set names for primaries only ,
upgoing wave , downgoing wave , and total response .
These data sets are in standard sis worktape format and
may be manipulated with the processing system. Only
the data set names desired should be entered. The
arrivals will be in the form of spikes with the
appropriate amplitudes which can then be filtered by
filt on the sun or sctvf on the cray.
-N vmod
Enter the name of the velocity model file (default is
stdin). The file contains 3 columns: layer thickness,
velocity (ft,m/s), density. The last entry for the
half space must have a negative layer thickness or
depth. If the velocity model is input here then use the
all-command line input method.
-C input
Enter the name of the optional file containing the
model input and control parameters. An example is
shown below:
SYNA test
1000 2 1 1 -1 02 4
1 1 1 1 -1 0
200 5000 1
500 6000 1.5
1000 7000 2.0
-1 8000 2.5
25 00 00 100
line 1: title
line 2: trace length (ms), sample interval, surface
reflection coefficient (water case=1, land case=-1),
upgoing source strength, downgoing source strength,
number depths for VSP, number layers in model. Note:
the sample interval can be in micro seconds also. In
this case all other times should be given in the same
units.
line 3: control flags. col 5: 1= receiver just above
free surface -1= receiver just below f.s.; col 6: 1=
print out equal travel time model 0=do not
line 4 - 7: input model (layer thichness or depth (ft
or m), velocity or slowness (ft or m/s), density).
final layer or halfspace is indicated by a negative
thickness.
line 8: initial source depth (ft or m), initial
receiver depth, depth increments for source and
receiver respectively
Most of these parameters with the exception of the velocity
model itself can also be entered on the command line (see -L
option below).
-n ntpr
Enter the number of traces per record. If the number
of depths is zero (usually true if only a surface
seismogram is desired) then the trace will be repeated
ntpr times.
-d Enter the command line argument '-d' if the model is
given in depth instead of thickness
-s Enter the command line argument '-s' if the model con-
tains slownesses instead of velocities
-m_to_ft
Enter the command line argument '-m_to_ft' if the model
has different units for velocity and depth. This
option changes m/s to ft/s.
-ft_to_m
Enter the command line argument '-ft_to_m' if the model
has different units for velocity and depth. This
option changes ft/s to m/s.
-P Enter the command line argument '-P' to get primaries
only
-D Enter the command line argument '-D' to just dump the
reflection coefficients vs depth to a seismic disk file
(given by -OP in this case). The number traces per
record will be given by the ntpr value. The number of
samples will be equal to the number of layers actually
found and the first sample output will correspond to
the first layer (regardless of its actual starting
depth).
-L Enter the command line argument '-L' to implememnt
optional command line input of parameters. This option
is useful if one is using the iconic processor XIKP to
run this program. In that case only the model itself
need be in a file, the rest of the parameters being
filled in by menu panel.
-gma Enter the command line argument '-gma' read in Amoco
GMA format well data.
-G input1
Enter the file name (including path name if necessary)
containing the GMA format well data.
-p rhogam
Enter the constant density to use for all depths.
Default = 1.0
-micro
Enter the command line argument '-micro' if time are
all in micro seconds, otherwise milli seconds is
assumed
-V Enter the command line argument '-V' to get additional
printout.
-? Enter the command line argument '-?' to get online
help. The program terminates after the help screen is
printed.
Optional Command line arguments
Using this option (-L) will allow the user to input most of
the required run time parameters via the command line except
for the velocity model itself and is the default mode when
running synth inside XIKP.
-L Enter the command line argument '-L' to input addi-
tional parameters via command line entry (also used in
XIKP synth process panel).
-T title
Enter the a string for a title (optional). If white
spaces are in the string the whole string must be
enclosed in double quotes.
-dt idelt
Enter the sample interval. Default = 2
-c0 ic0
Enter the surface reflection coefficient: 1 = water
case; -1 = land case. Default = 1
-eu iep
Enter the upgoing source strength. Default = 1
-ed iem
Enter the downgoing source strength. Default = -1
-od ndepth
Enter the number of depths for a VSP. Default = 1
-ol nlayer
Enter the number of interfaces in velocity model,
including the last negative thickness one. No default.
-B Enter the command line argument '-B' to put receiver
just below the free surface, otherwise the receiver
will be just above.
-sd xa0
Enter the initial depth of the source. Default = 0.
-rd xb0
Enter the initial depth of the receiver. Default = 0.
-dels dxa
Enter the depth increment for the source (VSP experi-
ment). Default = 0
-delr dxa
Enter the depth increment for the receiver (VSP experi-
ment). Default = 0
EXAMPLE 1
synth -Nvmod -OPprim -OUup -ODdown -OTtot -n1 -ls8000 -dt4
-ol4 -B -rd1.5 -n1
The velocity model is in file vmod and might look like
200 5000 1
500 6000 1.5
1000 7000 2.0
-1 8000 2.5
In the above 4-interface example we will generate 8 seconds
of data samples at 4ms with a receiver 1.5m below the free
surface (the water case is assumed). The output data sets
will contain 1 trace records.
EXAMPLE 2
synth -Cmodel_par -OPprim -OUup -ODdown -OTtot -n1 -ls8000
-dt4 -ol4 -B -rd1.5 -n1
The model parameter file -fImodel_par might look like
SYNA test
1000 2 1 1 -1 02 4
1 1 1 1 -1 0
200 5000 1
500 6000 1.5
1000 7000 2.0
-1 8000 2.5
25 00 00 100
In the above 4-interface example we will generate 1 seconds
of data samples at 2ms with a source 25 feet below the free
surface for the water case. The receiver starts just below
the free surface and will drop twice 100 feet at a time. The
output data sets will contain 1 trace records.
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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